Farmall 706 runs rough until warm

AOOC

Member
I have a 1963 gas Farmall 706, in good condition. No smoke, fluids kept changed, recent plugs and points, new float and needle valve in carb. My problem is that the tractor will start great, running on all cylinders and then after about three/ four minutes it starts to miss, occasional backfire, then eventually stall. Let it sit a minute and restart, same thing, becomes rough and stalls. I have restarted this tractor several times until it warms up and then it runs great the rest of the day. Gas flows well, I recently started to burn 93 octane, which I think might be the problem, but can't figure that that is causing the rough running until it gets warm.. Any help would be apprciated
 
What was your initial carb setting for the idle & load screws ?
The miss sounds like it may be starving for fuel at that one point. Maybe go out 1 turn on each & see how it acts.
 
Well NO the 93 is not the problem , You said you tuned it up , BUT did you put a timing light to it and set the ing. timing ?? here we need to know if it is a C 263 or a C 291 IF it is stock or does it have a C301 combine engine ?? Is your heat riser working??? More then likely the chamber below the heat riser is plugged full of carbon deposits and other then taking the exhaust manifold off the intake and digging and grinding the crud out there is no way of cleaning that i know of . Are you running the choke while you are warming it up as sometimes this is needed . Did you soak the carb in REAL carb cleaner or did you spray can clean it?? Does it have the solenoid on the carb or did someone remove it and put a adjusting screw in it because he was to cheap to replace the part?? One thing you do not want to do on them is try and ween them back. Have you checked the coil?? does it have the proper coil inplace ?? are you getting full fuel flow to the carb at all times??Have you run the valves ?? If you want it to run correctly then you have to check everything out . That is the long and short of it and one thing for sure i do know 706's.
 
I do not know on the "706" carb, but on the "H" carb the idle screw adjusts air, and turns counter-clockwise for lean. The main screw adjusts fuel, and turns clock-wise for lean. They are different. Not the way you might imagine. You might make double-sure which way is which on the "706".
 
To me, it sounds like a coil. Had this problem on a lot of gas tractors (because they never get changed). After it stalls, cautiously touch the coil (or use an infrared thermometer). If it's hot you likely have a bad coil. It will do exactly what you're saying. Starts fine, but after a few minutes it will start stalling and die. Let it sit for a bit and restart... then it will do the same.

A new coil doesn't necessarily exclude it as the issue. I've had bad ones out of the box.
 
A bad coil would not "run fine all day" after the engine had been warmed up.

These 6-cylinder engines have a reputation around my area as "cold blooded." You need to have your hand on the choke for the first several minutes, until the engine had adequately warmed up. Longer in winter. Especially any time you let out the clutch.
 
(quoted from post at 18:04:06 09/07/16) A bad coil would not "run fine all day" after the engine had been warmed up.

These 6-cylinder engines have a reputation around my area as "cold blooded." You need to have your hand on the choke for the first several minutes, until the engine had adequately warmed up. Longer in winter. Especially any time you let out the clutch.

I've had coils do similar before. Every so many starts it would run fine. Have you checked compression? I know my uncle's 706 liked to go through valves and would loose compression. Our 480 case had blown through the head gasket between cylinders and had a hard time running until it was warm. It would pool gas in the carb while cranking as it couldn't pull the mixture all the way up.
 
Thank-you for all the responses. Background it is a 263, and during the tune-up we did not replace the coil, so I may start with this. I should go over the carb and do real soak job, which I did not do since it looked pretty clean. When starting and it begins to run rough, choking does not help. The tractor just stalls out. This 706 never likes to run when it is cold, a little choke is always necessary until the temp comes up, then, good to go. However, based on all your suggestions, the issue I am dealing gives me some things to look at. I will let you know. Once again, appreciate the responses.
 
I had some issues with my 460 with water in the bottom of the carb..the drain screw/bolt for the float bowl was rounded over by too many channellocks and could not be removed until I got it apart and on the Bridgeport. It is the lowest point of the fuel system. After I dumped the bowl it ran better. Keeping the fuel as full as possible when the tractor sits idle seems to help a lot. Also the carb ices a lot of the time, and I have no heat shroud to help it.
 
(quoted from post at 21:38:21 09/07/16) Thank-you for all the responses. Background it is a 263, and during the tune-up we did not replace the coil, so I may start with this. I should go over the carb and do real soak job, which I did not do since it looked pretty clean. When starting and it begins to run rough, choking does not help. The tractor just stalls out. This 706 never likes to run when it is cold, a little choke is always necessary until the temp comes up, then, good to go. However, based on all your suggestions, the issue I am dealing gives me some things to look at. I will let you know. Once again, appreciate the responses.

Make sure to check your compression. Do you use lead additive or similar?
 

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